Boots – shoes – and leggings
Patent
1974-12-02
1979-12-04
Shaw, Gareth D.
Boots, shoes, and leggings
G06F 918, G06F 920
Patent
active
041775104
ABSTRACT:
Computer data and procedure protection by preventing processes from intering with each other or sharing each other's address space in an unauthorized manner is accomplished in hardware/firmware by restricting addressability to a segmented memory and by a ring protection mechanism.
To protect information in segments shared by several processes from misuse by one of these processes a ring protection hardware system is utilized. There are four ring classes numbered 0 through 3. Each ring represents a level of system privilege with level 0 (the innermost ring) having the most privilege and level 3 (the outermost ring) the least. Every procedure in the system has a minimum and a maximum execute ring number assigned to it which specifies who may legally call the procedure. Also maximum write and read ring numbers specify the maximum ring numbers for which a write and/or read operation is permitted.
Processes use a segmented address during execution wherein segment tables isolate the address space of the various processes in the system. Hardware checks that the address used by a process is part of the address space assigned to the process, and if the address is outside the prescribed address space, an exception occurs. A process cannot refer to data within the address space of another process because the hardware uses the segment table of the referencing process.
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Appell Marc
Bradley John J.
de Rivet Philippe-Hubert
Franklin Benjamin S.
Lepicard Georges
Compagnie Internationale pour l'Informatique CII Honeywell Bull
Rhoads Jan E.
Shaw Gareth D.
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